Radiodetector



April 10, 1928. 1,665,936

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W Ki I r ATTORNEY Patented Apr. 10, 1928.

UNITED STATES I I 1,665,936 PATENT OFFICE.

JOSEPH SLEPIAN, OF SWISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

RADIODETECTOR.

Application filed October 15, 1923. Serial-No. 668,554.

My invention relates to a transmission of intelligence by electricalmeans.

Broadly speaking, the object of my invention is to provide a moreconvenient form of detector for radio frequency signals.

Specifically, the object of my invention is to provide a detector whichshall be more convenient to use and more readily kept in adjustment thanthe detectors of the prior art.

In the prior art of the detection of radio signals, a number ofsubstances have beenfound to have such properties of unilateral.conductivity as to be sensitive to radio signals. In some of thesesubstances, this property is manifested only upon certain areas of thesurface of the substance, while with others, the sensitivity is moreuniformly dis-' tributed over the material, but is not high.

I have-found that a mixture made up of powdered carborundum, amorphouscarbon and a bonding agent such as kaolin or waterglass has the propertyof changing its effective resistance with a change in applied voltage,that is, its conductivity is non-rectilinear.

ing description and claims, when read in connection with theaccompanying drawings,

wherein:

Figure 1 is a diagrammatic View of a radio receiving system embodying myinvention.

Fig. 2 is a curve of the apparent change in resistance, with change inapplied voltage, of the material forming the detector of my device, and

Fig. 3 is a curve showing the change in current flow with change ofvoltage applied to the material forming the detector of my device.

In Fig. 1 is shown a receiving system comprisingan aerial 1, a tuninginductance 2, a ground 3, a signal receiver 4, a battery 5, a shuntingcondenser 6, a detector 7, connector wires 8 and 9 and a potentiometer10.

The detector 7 consists of conducting plates 11 and 12 on opposite sidesof a mass a given current and that an increase in voltage produces morethan a proportional increase in current over a range of a few appliedvolts. 7

In operation, the potential battery 5 is adjusted, by means of thepotentiometer 10, until the voltage drop across the mass 14 of detector7 is such as to bring the current value to the bend of the curve of Fig.3, indicated by point a. The circuit comprising aerial 1, tuninginductance 2 and ground 3 is then brought into resonance with theincoming signals. Upon the arrival of signals, high frequency isimpressed across the terminals of detector 7 by way of connecting leads8 and 9 and The potential of battery 5 having been adjusted to providean applied potential across shunting condenser rent t rough the signalindicator 4 and hat-.

tery 5 by virtue of the non-rectilinear conductivity of the detector inthe following manner.

If the first half cycle of the high frequency current happens to have apolarity which is additive with the applied voltage of the polarizingbattery, raising the voltage to point 0, the increased voltage bringsinto effect the reduction of resistance with increased voltage, and acurrent larger than is proportionate to the previous voltage and currentwill flow from battery 5 through phones 4, detector 7 and the circuit,as shown by point d. The next half cycle of the highfrequency currentwill be in opposition to the battery voltage and therefore subtractive,producin a voltage corresponding to point e. The lower voltage willbring into play the efl'ectively higher resistance of the etector 7.Since the effective resistance of the material is higher, a reduction incurrent from battery 5 through signal indicator 4: to point f willoccur, which reduction will, however, be proportionately less in valuethan the increase in current produced by the preceding half cycle. 'Inthis Way, the presence of a high-frequency current in the circuitinfluences the average current flowing 'from battery 5, causing anincrease in its value equal to the difference between the in creaseproduced by one half wave over the decrease produced by the other halfWave of the received signal, which occurs during the period of thereception of the signal. The increase of current during the time of thesignal produces an effect on the signal indicator 4, therebyrenderingthe signal perceptible.

In this wa my device, in operation,

gives rectification and detection of incoming radio frequency signals.

body comprising a mixture of carborundum,

amorphous carbon and a binder.

2. A radio detector comprising a body having a non-rectilinearconductivity, said body comprising a mixture of powdered carborundum,lampblack and a bonding agent, said bonding agent comprising sodiumsilicate.

In testimony whereof, I have hereunto subscribed my name this 9th day ofOctober,

JOSEPH SLEPIAN.

